1. Technical Field
The invention relates generally to an improved vehicle suspension system. More particularly, the invention relates to an improved vehicle suspension system for use with light and medium duty trailers. More specifically, the invention relates to a suspension system for light and medium duty trailers which utilizes enclosed diaphragms to provide vertical support between the trailer and the axle.
2. Background Information
The trucking industry has witnessed a dramatic increase in the costs associated with transporting goods. Additionally, there has been on increase in the sale of pickup style trucks and sport utility vehicles assuring that a much broader range of people have vehicles with the capacity to pull light and medium duty trailers. The need to pull light and medium duty trailers has also increased with the associated increase in the growth of small businesses throughout the world. These changes in the trucking industry, and in the number of people interested in purchasing and subsequently using light and medium duty trailers necessitates the need for an efficient and relatively inexpensive suspension system for use on light and medium duty trailers.
Suspension systems may take a variety of forms, including parallelogram suspensions and leading and trailing beam type suspensions, any of which may utilize either mechanical springs, air springs or a combination of both mechanical springs and air springs. In the past, light and medium duty trailers often utilized mechanical springs and/or torsion tubes as a way of taking up the necessary movement between the axle and the trailer frame while supporting the vertical loads associated with the trailer. Mechanical springs often took the form of coil leaf springs, variations on sear springs, and coil springs.
Additionally, torsion tubes were often utilized and often took the form of an axle with one or more rubber components whereby movement of the axle relative to the trailer was taken up by twisting or deflecting the rubber components. While these method of operation were presumably adequate for the purpose for which they were intended, they do not provide the smooth even ride of an air type suspension system, and also do not provide for load leveling characteristics commonly associated with air type suspension systems. While air type suspension systems have been contemplated for light and medium duty trailers, the cost of such systems has been somewhat high when compared to the limited cost of light and medium duty trailers and as such, have never gained wide acceptance.
A number of the problems associated with air ride suspension systems on light and medium duty trailers include the cost of the air spring and the necessary mechanical linkages to control the movement of the air spring. These costs are relatively high compared to existing mechanical style suspension systems. Additionally, air springs, or air bladders, support vertical load and provide a dampening between the axle and the trailer frame. However, air bladders themselves provide no resistance lateral and longitudinal deflection and therefore must be artificially stabilized by mechanical linkages extending between the axle and the frame to isolate the air spring and assure that the air spring provides only vertical support and dampening. These linkages coupled with relatively high initial cost and replacement cost of air springs made air ride suspension systems for light and medium duty trailers too costly for widespread acceptance.
The need thus exists for an air ride suspension system for light and medium duty trailers which provides for an air bladder which is stable and which adequately provides a dampening force between movement of the axle relative to the trailer frame while simultaneously supporting the vertical load associated with the trailer.